1. Field of the Invention
This invention relates to a process and an apparatus for producing carbon fibers having good performance with good production efficiency.
2. Description of the Prior Art
Carbon fibers obtained by preoxidizing and carbonizing fibers of organic polymers such as regenerated cellulose fibers or polyacrylonitrile fibers under specified conditions have found a variety of applications, for example, as reinforcing materials for composite materials because of their high tenacity, high Young's modulus, low specific gravity, chemical resistance and other superior properties, as described in detail, for example, in M. Langley "Carbon Fibres in Engineering", McGraw-Hill Book Co., (U.K.) Limited., 1973.
Usually, carbon fibers are produced by first preoxidizing fibers of organic polymers at 200.degree. to 300.degree. C in air or in an atmosphere of another oxidizing gas, and then carbonizing the preoxidized fibers at 1,000.degree. to 2,000.degree. C in an atmosphere of an inert gas such as nitrogen or argon.
In order to obtain high performance carbon fibers, various improvements have been proposed in the art in the choice of the composition of the starting polymer and in the prescription of the conditions for the preoxidation and carbonization, such as the ambient atmosphere, the temperature, the time, and the tension of fibers, and improvements have also been made in changing batch processes to continuous processes.
Since in the early stage of carbonization, high amounts of volatile components are generated which cause process troubles as a result of becoming tarry, it is especially important to prevent such from occurring. It is also important to remove oxygen from the ambient atmosphere using the minimum amount of an inert gas, and also to prevent the breakage of fiber strands and the consequent occurrence of fiber fuzz during the production of carbon fibers.